The present invention pertains to a high-power pressure wave source for generating individual, high-energy pressure waves that can be repeated at short intervals of time, each time by igniting a defined volume of a combustible fluid mixture as well as by increasing its rate of combustion up to detonation.
Pressure and shock waves of relatively low power (about 10 to 100 mJ) have been known especially from medical engineering, e.g., in the form of lithotriptors. Current versions usually operate according to the electromagnetic principle, generating flat, focusable pressure waves by means of a coil/membrane unit.
For nonmedical, especially industrial applications, there is a need for a substantially higher pressure wave energy (about 50 to 100 times higher energy). A simple enlargement/scale-up of the prior-art electromagnetic shock wave sources is not meaningful because of their poor efficiency.
DE-OS 39 21 808 discloses a device for the focused shock wave treatment of tumors, with various possibilities of shock wave generation, e.g., by means of an explosive gas mixture (see claim 10). However, no indications of the design embodiment of this principle are given.
Pressure waves are also generated in reciprocating piston motors by the ignition of combustible fluid mixtures, and the ignition process can be repeated at short intervals of time as often as desired. The fluid mixture, at least the air component, is greatly compressed (factor  greater than 10), and the combustion is initiated by electric spark ignition or by injecting the fuel. A xe2x80x9csoft,xe2x80x9d not too rapid combustion is generally desired, because detonation-like combustion processes would mechanically overload the components of the motor (pistons, connecting rod, bearings, etc.). The transmission of this principle of compression to other pressure wave sources would be relatively complicated in terms of design and energy, i.e., rather uneconomical.
It has been known that hydrogen-air mixtures can be ignited under atmospheric pressure and that the initially slow, laminar combustion (deflagration) can be accelerated by slightly increasing the pressure by fluidic measures (vortex generators/flow obstacles) via a rapid, turbulent combustion up to the detonation with high pressure peaks. This principle is utilized in experimental techniques to simulate the conditions and loads possibly occurring in the reactor building during nuclear power plant accidents (core melt-through, release of hydrogen). See the journal xe2x80x9cNACHRICHTENxe2x80x9d Forschungszentrum Karlsruhe, Vol. 28 (1996), No. 2-3, pp. 175-191. Large, tubular or channel-like combustion chambers with lengths of 12 m and 70 m and with variable, fluidically effective built-in units/geometries were built for this purpose, the smaller unit (FZK) being in Germany and the larger (RUTT) in Russia.
Based on the principle of combustion acceleration to detonation, which was embodied in large dimensions there, the primary object of the present invention is to provide a high-power pressure wave source with short pulse duration and good repetition rate, which is relatively simple, manageable, robust and inexpensive and operates safely, reliably, and economically.
According to the invention, a high-power pressure wave source for generating individual, high-energy pressure waves is provided. The generation of the waves can be repeated at short intervals of time, each time by igniting a defined volume of a combustible fluid mixture as well as by increasing its rate of combustion up to detonation. A channel of a defined length, which expands in cross section toward one of its two ends is provided to form a combustion chamber. A feed means is provided for the components of the fluid mixture, and an igniting means is provided in the area of the narrow end of the channel. A discharge means is provided for the waste gas in the area of the second end of the channel, and a said membrane is provided which closes the wide end of the channel on the front side and forms an acoustic transmission element. Further, a plurality of vortex generators are distributed over the length of the channel.
The pressure wave source comprises a combustion chamber in the form of a channel of a defined length with an end of enlarged cross section. The front-side closure of the wide channel end forms a membrane acting as an acoustic transmission element, wherein a discharge means for the waste gas is present in the area of the membrane. The narrow channel end is used to feed the components of the mixture and for ignition. The vortex generators, which accelerate the combustion process up to the detonation, are provided between the narrow and wide ends of the channel. It is achieved due to the geometric/volumetric conditions that the majority of the mixture is located in the area of the membrane, burns off there in a detonation-like manner, and thus brings about the pressure wave generation. Any desired, acoustically conductive medium (e.g., solid, gel-like, rubber-like) may be in contact with the membrane during use. Elements for focusing the pressure waves originating from the membrane may be joined as well.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.